Re: Note describing poor dcache utilization under high memory pressure

[Linus Torvalds]

On Tue, 29 Jan 2002, Oliver Xymoron wrote:
>
> fork:
>   detach page tables from parent

 - leave the option ot just mark them read-only on architectures that
   support it (ie x86, I think alpha does this too).

>   retain pointer to "backing page tables" in parent and child
>   update use count in page tables

You want to copy the top-level page table directory (with the "present
bit" disabled or something), not just retain a pointer to it. Otherwise
you just get really confused after two fork() calls, where you can have
multiple "backing page tables".

>   "prefault" tables for current stack and instruction pages in both parent
>     and child

Don't unconditionally prefault. There are many potentially useful things
that do _not_ want to do this, for example snapshot creation.

So the generic "do_fork()" thing should _not_ do prefaulting, although
"sys_fork()"  may well choose to do it.

			Linus